Apparatus for manufacturing molten irons to improve operation of fluidized bed type reduction apparatus and manufacturing method using the same

ABSTRACT

The invention relates to an apparatus and method for manufacturing molten iron. The method for manufacturing molten iron includes producing a mixture containing iron by drying and mixing iron-containing ore and additives, passing the mixture containing iron through one or more successively-connected fluidized beds so that the mixture is reduced and calcined to thereby perform conversion into a reduced material, forming a coal packed bed, which is a heat source in which the reduced material has been melted, charging the reduced material to the coal packed bed and supplying oxygen to the coal-packed bed to manufacture iron, and supplying reduced gas exhausted from the coal-packed bed to the fluidized bed, wherein in the conversion of the mixture to a reduced material, oxygen is directly supplied and combusted in an area where reduced gas flows to the fluidized bed. The apparatus for manufacturing molten iron of the invention uses this method for manufacturing molten iron. Through use of the invention, the reduced gas passing through the fluidized beds may be improved, and cohesion of the iron-containing fine ores may be prevented.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The invention relates to an apparatus and method for manufacturingmolten irons, and more particularly to an apparatus and method formanufacturing molten irons that supplies oxygen and water to afluidized-bed reactor for increasing a temperature in the fluidized-bedreactor to thereby manufacture molten irons.

(b) Description of the Related Art

The iron and steel industry is a core industry that supplies the basicmaterials needed in construction and in the manufacture of automobiles,ships, home appliances, and many of the other products we use. It isalso an industry with one of the longest histories that has advancedtogether with human progress. In an iron foundry, which plays a pivotalroll in the iron and steel industry, after molten iron (i.e., pig ironin a molten state) is produced using iron ore and coal as raw materials,steel is produced from the molten iron and is then supplied tocustomers.

Approximately 60% of the world's iron production is realized using theblast furnace method developed in the 14th century. In the blast furnacemethod, cokes produced using iron ore and bituminous coal that haveundergone a sintering process as raw materials are placed in a blastfurnace, and oxygen is supplied to the furnace to reduce the iron ore toiron to thereby manufacture molten iron. The blast furnace method, whichis a main aspect of molten iron production, requires raw materialshaving a hardness of at least a predetermined level and grain size thatcan ensure ventilation in the furnace. Coke in which specific raw coalthat has undergone processing is needed as a carbon source to be used asfuel and a reducing agent. Also, sintered ore that has undergone asuccessive compacting process is needed as an iron source. Accordingly,in the modern blast furnace method, it is necessary to include rawmaterial preparation and processing equipment such as coke manufacturingequipment and sintering equipment. Therefore, not only is it necessaryto obtain accessory equipments in addition to the blast furnace, butequipment to prevent and minimize the generation of pollution in theaccessory equipment is needed. The amount of investment, therefore, isconsiderable, ultimately increases manufacturing costs.

In order to solve these problems of the blast furnace method,significant effort is being put forth in iron foundries all over theworld to develop a smelting reduction process that produces molten ironsby directly using fine coal as fuel and as a reducing agent, and alsodirectly using fine ores, which are used in over 80% of the world's oreproduction, as an iron source.

As an example of such a smelting reduction process, U.S. Pat. No.5,584,910 discloses a method of manufacturing molten iron that directlyuses fine coals and fine ores. A method is disclosed in this patent forproducing a molten pig iron or molten steel preliminary product from acharge material that partially includes fine iron ores. The fine ironores are directly reduced into sponge irons in at least onefluidized-bed reactor, and the sponge iron is melted in a melting regionby supplying carbon carriers and an oxygen containing gas. Reduced gasthat is generated in this process is provided to the fluidized-bedreactors, then is exhausted as an exhaust gas after undergoing reaction.

When compared to the conventional blast furnace method, since the abovemethod for manufacturing molten iron uses fine iron ores and fine coalsinstead of lump ores and cokes, the advantage is realized in which therange of grain sizes of raw coal is wide. Further, equipment stoppagesand re-starting are easy. However, as a result of using the fine ironores as raw material and also using multiple stages of fluidized-bedreactors, it is not easy to adjust an inner state of the fluidized-bedreactors, and in particular, an inner temperature thereof.

Accordingly, in order to adjust an inner temperature of thefluidized-bed reactors, a method is used in which a separate combustionchamber and burner are provided to an exterior of the fluidized-bedreactors to thereby increase the temperature of a gas supplied to thefluidized-bed reactors. However, when the reaction gas that is increasedin temperature passes through a dispersing plate provided to induceuniform gas flow in the fluidized-bed reactors, ore particles containedin the reaction gas form a compound having a low melting point such thatthe dispersing plate becomes blocked, thereby making it impossible toperform fluidized bed reduction process.

SUMMARY OF THE INVENTION

The invention has been made in an effort to solve the above problems.The present invention provides an apparatus and method for manufacturingmolten iron that supplies oxygen and water directly to a fluidized-bedreactor to increase a temperature of a reaction gas and prevent moltenfine ores from adhering to the fluidized-bed reactor thereby improvingoperation of the fluidized-bed reactor.

The method for manufacturing molten iron includes the steps of producinga mixture containing iron by drying and mixing iron ores and additives;passing the mixture containing iron through one or moresuccessively-connected fluidized beds so that the mixture is reduced andcalcined to thereby perform conversion into a reduced material; forminga coal packed bed, which is a heat source in which the reduced materialhas been melted; charging the reduced material to the coal packed bedand supplying oxygen to the coal packed bed to manufacture molten irons;and supplying reduced gas exhausted from the coal packed bed to thefluidized bed, wherein in the step of converting the mixture to thereduced material, oxygen is directly supplied and combusted in an areawhere reduced gas flows to the fluidized bed.

In the step of converting the mixture containing iron to a reducedmaterial, water may be supplied separately from the oxygen supplycombustion process and then be mixed with the oxygen.

Preferably, the water is one of process water and steam.

The water may be supplied at a rate of 300˜500 Nm³/hr.

Preferably, the oxygen is supplied and combusted in the case where aninternal temperature of a fluidized-bed reactor is 650° C. or higher.

The step of converting the mixture containing iron to a reduced materialincludes (a) pre-heating the mixture containing iron in a firstfluidized bed; (b) performing preliminary reduction of the pre-heatedmixture containing iron in a second fluidized bed; and (c) performingfinal reduction of the mixture containing iron that has undergonepreliminary reduction to thereby realize conversion into the reducedmaterial. The oxygen is directly supplied and combusted in the step (a)and the step (b).

Oxygen may be supplied and combusted immediately prior to steps (a),(b), and (c).

The apparatus for manufacturing molten iron includes one or morefluidized-bed reactors that reduce and calcine iron ores and additiveswhich are dried and mixed to convert into a reduced material; amelter-gasifier for charging the reduced material and receiving thesupply of oxygen to manufacture molten irons; and a reduced gas supplyline for supplying reducing gas exhausted from the melter-gasifier tothe fluidized-bed reactors, wherein the fluidized-bed reactors eachinclude a dispersing plate at a lower area thereof and through which thereduced gas passes, and an oxygen burner mounted to an outer wall of thefluidized-bed reactor at an area above the dispersing plate.

The oxygen burner includes a first member inside of which coolantcirculates in a lengthwise direction; and a second member encompassed bythe first member along a lengthwise direction in a state separated fromthe same, and inside of which coolant is circulated. Preferably, oxygenis supplied and combusted between the first member and the secondmember, and a distance between the first member and the second member isgetting reduced as coming close to the inside of fluidized-bed reactor.

The fluidized-bed reactors may each include a water supply nozzlemounted to an outer wall of the fluidized-bed reactor at an area abovethe dispersing plate, and positioned at an area in the vicinity of theoxygen burner.

A direction that the water supply nozzle supplies water is preferably atan angle of 4˜15° with respect to the lengthwise direction of the oxygenburner.

The water may be one of process water and steam.

The water may be atomized and supplied at a rate of 300˜500 Nm³/hr.

The fluidized-bed reactors may include a pre-heating furnace forpre-heating the mixture containing iron; a preliminary reduction furnaceconnected to the pre-heating furnace and performing preliminaryreduction of the pre-heated mixture containing iron; and a finalreduction furnace connected to the preliminary reduction furnace andperforming final reduction of the mixture containing iron that hasundergone preliminary reduction to thereby realize conversion into thereduced material, wherein an oxygen burner is included in each of thepre-heating furnace and the preliminary reduction furnace.

Each of fluidized-bed reactors may further include a water supply nozzlemounted to an outer wall of the fluidized-bed reactor at an area abovethe dispersing plate, and positioned in the vicinity of the oxygenburner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an apparatus for manufacturing molten ironaccording to a first embodiment of the invention.

FIG. 2 is a partial sectional view of an oxygen burner according to afirst embodiment of the invention.

FIG. 3 is a schematic view of an apparatus for manufacturing molten ironaccording to a second embodiment of the present invention.

FIG. 4 is a partial sectional view of an oxygen burner and a watersupply nozzle according to a second embodiment of the invention.

FIG. 5 is a graph showing changes in an oxygen flame temperature as afunction of water supply amount according to an experimental example ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention will now be described in detailwith reference to the accompanying drawings. Many variations and/ormodifications of the basic inventive concepts may appear to thoseskilled in the present art. The embodiments are to be regarded asillustrative in nature, and not restrictive.

FIG. 1 is a schematic view of an apparatus for manufacturing molten ironaccording to a first embodiment of the invention. The apparatus is shownin a state where oxygen burners are mounted to fluidized-bed reactors.

An apparatus 100 for manufacturing molten iron according to a firstembodiment of the invention includes the main elements of afluidized-bed reactor unit 20, a melter-gasifier 10, and other accessoryequipments. The fluidized-bed reactor unit 20 includes one or morefluidized-bed reactors having a fluidized bed therein, and acts toreduce and calcine iron ores and additives to reduced material. Thereduced material is charged to the melter-gasifier 10, which includes acoal packed bed therein, and oxygen is supplied to the melter-gasifier10 to thereby produce molten irons. Reduced gas exhausted from themelter-gasifier 10 is used to reduce and calcine iron ores and additivesby passing through the fluidized-bed reactors after being supplied tothe same via a reduced gas supply line L55, after which the reduced gasis exhausted to the outside.

Elements included in the apparatus 100 for manufacturing molten ironaccording to the first embodiment of the invention will now be describedin more detail.

After temporarily storing fine ores containing iron and additives of agrain size of 8 mm or less at room temperature, the fluidized-bedreactor unit 20 removes water from these elements in a drier 22 andmixes the same to produce a mixture that contains iron. The mixturecontaining iron manufactured in this manner is charged to thefluidized-bed reactors. An intermediate vessel 23 is provided betweenthe drier 22 and the fluidized-bed reactors such that the ironcontaining mixture at room temperature is charged to the fluidized-bedreactors that are maintained at a pressure from a normal pressure to1.5˜3.0 atmospheres.

As shown in FIG. 1, the fluidized-bed reactors in the first embodimentof the present invention are realized through three stages. This numberof the fluidized-bed reactors is for illustrative purposes only and isnot meant to restrict the invention. Accordingly, a variety of differentnumbers of stages may be used for the fluidized-bed reactors.

The fine ores containing iron and additives supplied to thefluidized-bed reactors form a fluidized bed by contacting a hightemperature reduced gas current, and is converted into a hightemperature reduced material that is at a temperature of 80° C. or more,is 80% or more reduced, and is 30% or more calcined. As shown in FIG. 1,in a first stage of the fluidized bed reduction process, the ironcontaining mixture at room temperature is pre-heated in a pre-heatingreactor 24. Next, in a second stage, preliminary reduction of thepre-heated mixture containing iron is performed in a preliminaryreducing reactor 25, which is connected to the pre-heating reactor 24.Finally, in a third stage, the iron containing mixtures that are reducedin the preliminary reducing reactor 25 undergoes final reduction in afinal reducing reactor 26, which is connected to the preliminaryreducing reactor 25.

Although not shown in FIG. 1, to prevent scattering loss when reducedmaterial exhausted from the fluidized-bed reactors is directly chargedto the melter-gasifier 10, a hot compacting apparatus may be mountedbetween these elements. Further, a hot intermediate vessel 12 isprovided for supplying the reduced material exhausted from thefluidized-bed reactors to the melter-gasifier 10 to thereby make supplyof the reduced material to the melter-gasifier 10 easy.

Lump coal or shaped coal realized by compressing fine coal is suppliedto the melter-gasifier 10 to form a coal packed bed. The lump coal orshaped coal supplied to the melter-gasifier 10 is gasified by apyrolysis reaction at an upper area of the coal-packed bed and by acombustion reaction using oxygen at a lower area of the coal-packed bed.Hot reduced gas generated in the melter-gasifier 10 by the gasifiedreaction is supplied in succession to the fluidized-bed reactors throughthe reduced gas supply line L55, which is connected to a rear end of thefinal reducing reactor 26, to be used as a reducing agent and fluidizedgas.

A dome-shaped empty space is formed to an area above a coal packed bedof the melter-gasifier 10. The flow rate of gas is reduced by the emptyspace such that large amounts of fine ores included in the chargedreduced material and fine ores generated as a result of an abruptincrease in temperature of coal charged in the melter-gasifier 10 areprevented from being discharged out of the melter-gasifier 10. Further,such a configuration allows for absorbing of variations in pressure inthe melter-gasifier 10 caused by irregular changes in the amount of gasgenerated as a result of directly using coal. The coal is gasified andremoves volatile matters while dropping to the bottom of the coal packedbed, and ultimately is burned by oxygen supplied through tuyeres at thebottom of the melter-gasifier. The generated combustion gas raisesthrough the coal packed bed, and is converted into high temperaturereduced gas and exhausted to outside the melter-gasifier 10. Part of thecombustion gas is scrubbed and cooled while passing through watercollecting devices 51 and 53 such that pressure applied to themelter-gasifier 10 is maintained within the range of 3.0˜3.5atmospheres.

A cyclone 14 collects exhaust gas generated in the melter-gasifier 10such that dust is again supplied to the melter-gasifier 10, and gas issupplied as reduced gas to the fluidized-bed reactors through thereduced gas supply line L55. Reduced iron drops within the coal packedbed together with the coal to undergo final reduction and smelting bycombustion gas and combustion heat generated by gasifying and combustingcoal, after which the iron is exhausted to the outside.

Since reduced gas exhausted from the melter-gasifier 10 slowly decreasesin temperature while passing through the fluidized-bed reactors,additional oxygen supply apparatuses 71, 72, and 73 are provided in thesystem. Oxygen is supplied by the oxygen supply apparatuses 71, 72, and73 to be partially combusted, and the reduced gas is increased intemperature using the combustion heat while maintaining a suitable levelof oxidation of the reduced gas.

In the first embodiment of the invention, in order to prevent reducedgas raised in temperature from damaging or blocking a dispersing platemounted to a lower area of the fluidized-bed reactors and through whichreduced gas passes, to oxygen is directly supplied to and combusted inan area where reduced gas flows to fluidized beds of the fluidized-bedreactors. To realize this in the invention, as shown in the enlargedcircle of FIG. 1, an oxygen burner 60 is mounted to an exterior wall ofeach of the fluidized-bed reactors at an area above a dispersing plate27. Therefore, the reduced gas is minimally increased in temperature bythe oxygen supplied through the oxygen supply apparatuses 71, 72, and73. Also, it is possible to further increase the temperature of thereduced gas by operation of the oxygen burners 60.

In the case where oxygen is supplied and combusted through the oxygenburner 60 shown in the enlarged circle of FIG. 1, a combustion area 44is formed in the vicinity of the oxygen burner 60. In the firstembodiment of the invention, oxygen is directly supplied to andcombusted in the area where reduced gas flows to the fluidized beds inthe fluidized-bed reactors. Accordingly, with the formation of thecombustion area 44 in the area where the fluidized beds are formed wherethe dispersing plate 27 is already passed, any negative affect given tothe dispersing plate 27 is minimized.

In the first embodiment of the invention, one of the oxygen burners 60is preferably mounted to the pre-heating reactor 24 and to thepreliminary reducing reactor 25 for direct supply and combustion ofoxygen. Since a reduction rate of the iron containing mixtures forming afluidized layer is not very high in the pre-heating reactor 24 and thepreliminary reducing reactor 25, even if contact is made with the oxygenflame, molten cohesion of the iron containing mixture is not verysignificant. In contrast to this, material forming the fluidized bedsreaches a reduction rate of a predetermined level in the final reducingreactor 26 such that there is concern for molten cohesion of the finedirect reduced iron such that oxygen is preferably not directly suppliedto the final reducing reactor 26.

In addition, in the case where an internal temperature of thepre-heating reactor 24, the preliminary reducing reactor 25, and thefinal reducing reactor 26 (i.e., in the fluidized-bed reactors) is 650°C. or greater, it is preferable that oxygen is supplied through theoxygen burners 60. If the oxygen burners 60 are operated to supplyoxygen when the internal temperature of the fluidized-bed reactors isless than 650° C., part of the supplied oxygen is not burned and isinstead mixed and flows with the reduced gas to reduce the reductionrate of the iron containing mixture. The oxygen burners 60 will bedescribed in greater detail with reference to FIG. 2.

FIG. 2 is a partial sectional view of one of the oxygen burners 60according to the first embodiment of the invention. Since an exterior ofthe oxygen burner 60 is easily understood by those skilled in the art,only a sectional view of this element is shown.

As shown in FIG. 2, the oxygen burner 60 is formed in a double pipestructure. The oxygen burner 60 includes a first member 601 inside ofwhich coolant circulates in a lengthwise direction, and a second member611 encompassed by the first member 601 along a lengthwise direction ina state separated from the same, and inside of which coolant iscirculated. The second member 611 includes a flame sensor 616 providedto one end. The oxygen burner 60 may include additional devices requiredfor oxygen. Oxygen is supplied between the first member 601 and thesecond member 611, and, as shown in FIG. 2, a distance between the firstmember 601 and the second member 611 is getting reduced as coming closeto the inside of fluidized-bed reactor (i.e., in the direction of thearrows) such that oxygen is combusted while being sprayed at a highpressure. Further, the oxygen is concentrated toward a center positionfor supply and combustion such that the oxygen is sprayed deep into thefluidized bed in the fluidized-bed reactor while a flame is effectivelyformed.

Cooling pipes 602 and 612 are formed respectively in the first member601 and the second member 611 to protect the oxygen burner 60 from thehigh temperature oxygen flame. A coolant is supplied and circulatedthrough the cooling pipes 602 and 612.

The flame sensor 616 mounted to one end of the second member 611 detectswhether the oxygen supplied to within the fluidized bed has beencombusted. The flame sensor 616 detects an oxygen flame within a matterof seconds during oxygen supply, and continuously maintains the oxygenflame. By the installed flame sensor 616, there is no concern of adecrease in the reducing rate of the reducing gas by oxygen not beingcombusted and mixed with the reducing gas, or of the oxygen that is notcombusted converting in one area and exploding.

A second embodiment of the invention will be described below withreference to FIGS. 3 and 4.

FIG. 3 is a schematic view of an apparatus for manufacturing molten ironaccording to a second embodiment of the invention. The apparatus isshown in a state where oxygen burners and water supply nozzles aremounted to fluidized-bed reactors.

An apparatus 200 for manufacturing molten iron according to a secondembodiment of the invention is identical to the apparatus of the firstembodiment except for the water supply nozzles. Therefore, anexplanation of these identical elements will not be provided and thedescription will be concentrated on the water supply nozzles.

As shown in the enlarged circle of FIG. 3, the apparatus 200 formanufacturing molten iron according to the second embodiment of theinvention includes a water supply nozzle 65 positioned in the vicinityof the oxygen burners 60 mounted to the outer wall above the dispersingplate 27 in each of the fluidized-bed reactors. The fluidized-bedreactors may include additional equipment as needed.

The water supply nozzle 65 mixes and supplies water to the oxygen flamesupplied and formed through the oxygen burner 60 to thereby form acombustion area 46. Accordingly, a temperature of the oxygen flame maybe reduced such that molten cohesion of reduced iron in a hightemperature area by direct contact to the oxygen flame or by the oxygenflame is minimized. In addition, by the reduction in the temperature ofthe oxygen flame, damage to the material positioned opposite where theoxygen flame is formed is decreased.

FIG. 4 is a partial sectional view of one of the oxygen burners and itscorresponding water supply nozzle according to the second embodiment ofthe invention. Since the oxygen burner 60 is identical to that of thefirst embodiment of the invention, a detailed description thereof isomitted. The water supply nozzle 65 is structured including a pipemember 651 with an aperture 652 formed therein. Water is suppliedthrough the aperture 652 separately from the oxygen and mixed into theoxygen flame.

In FIG. 4, although the water supply nozzle 65 is shown positioneddirectly over the oxygen burner 60, such a configuration is shown merelyto illustrate the invention and is not meant to limit the same.Accordingly, it is only necessary that the water supply nozzle 65 bepositioned in the vicinity of the oxygen burner 60.

At least one of process water and steam used in the process tomanufacture molten iron may be individually or jointly mixed then usedduring oxygen supply and combustion. In this case, the temperature ofthe oxygen flame is not only reduced, but as a result of water shiftreaction resulting from an oxygen flame of a maximum temperature, thesupplied process water or steam is separated into its elements of oxygenand hydrogen. The oxygen is combusted in the oxygen flame, and thehydrogen is included in the reduced gas to aid in the reduction reactionof the iron containing mixture. In particular, hydrogen is mainly usedas a reducing agent in methods to manufacture molten iron, and is apowerful reducing agent that has approximately four times the reducingstrength of carbon monoxide. Therefore, water supply is highlypreferable.

Water atomized and supplied through the water supply nozzle 65 ispreferably supplied at a rate of 300˜500 Nm³/hr. If water is notatomized and supplied, and instead directly supplied, a water shiftreaction or a cooling effect of combustion gas is unable to be obtained.

If the supply rate of water is less than 300 Nm³/hr, the oxygen flametemperature is unable to be reduced. Further, the amount of resolvedoxygen and hydrogen is small such that the water supply effect isminimal and the oxygen supply flow rate of the oxygen burner 60 is low,thereby possibly causing malfunction of the oxygen burner 60. If theamount of water supplied exceeds 500 Nm³/hr, an amount of water of morethan needed contacts the oxygen flame to reduce the heating effect ofthe fluidized beds by the oxygen flame by half. In addition, water thatdoes not participate in the water shift reaction and is left remainingin a steam state acts as a binder to thereby possibly cause cohesion ofthe iron containing mixture.

In the second embodiment of the invention, the water supply nozzle 65 ismounted such that a direction along which it supplies water is set at anangle (θ) of 4˜15° with respect to a lengthwise direction of the oxygenburner 60. As shown in FIG. 4, in the case where the water supply nozzle65 is provided above the oxygen burner 60, it is preferable that thewater supply nozzle 65 is slanted downwardly 4˜15°. If the angle (θ) isless than 4°, the point at which contact is made to the oxygen flame isfurther extended into the fluidized bed or does not contact the oxygenflame at all. If the angle (θ) exceeds 15°, not only is the supply pathof the oxygen flame obstructed, but the amount of time to reach theoxygen flame is too short such that a reduction in temperature of theoxygen flame and the water shift reaction cannot be expected.

The invention will be described in greater detail below through anexperimental example. This experimental example merely illustrates theinvention and is not meant to limit the invention.

EXPERIMENTAL EXAMPLE

At the same time oxygen is supplied through the oxygen burner, water issupplied through the water supply nozzle to adjust the water supplyamount according to the second embodiment of the invention. A simulatingexperiment was performed to measure the resulting oxygen flametemperature. The water supply amount is measured using a flow meter, andthe oxygen flame temperature is measured using a UV thermometer.

The test results are shown in FIG. 5. FIG. 5 is a graph showing changesin an oxygen flame temperature as a function of water supply amountaccording to the experimental example of the invention. In theexperimental example of the invention, an atmospheric temperature is setat 600° C. or greater such that an oxygen flame is generated, but sincethis is a test with respect to an oxygen flame in atmosphere, there maybe a difference in the absolute temperature value. However, thereduction in temperature may be predicted as shown in the graph of FIG.5.

As shown in FIG. 5, in the case where water is supplied to inside theoxygen flame at a rate of approximately 300 Nm³/hr, the temperature ofoxygen flame was reduced from about 2700° C. to about 2000° C. Theamount of oxygen and the amount of hydrogen generated in this case wereeach approximately 300 Nm³/hr. Also, in the case where water is suppliedto inside the oxygen flame at a rate of approximately 500 Nm³/hr, theoxygen flame was reduced from about 2700° C. to about 1500° C. Theamount of oxygen and the amount of hydrogen generated in this case wereeach approximately 500 Nm³/hr.

In analyzing the relation between oxygen flame temperature to the watersupply amount in this Experimental Example, it is clear that for every 1Nm³/hr of water that is supplied, the temperature of the oxygen flame isreduced by approximately 2.53° C.

Since in the invention oxygen is directly supplied to an area wherereduced gas flows to fluidized beds, not only is the negative impactgiven to the dispersing plate minimized, but the rate of reduction ofthe iron containing mixture is increased by increasing the temperatureof the reduction gas. Therefore, the quality of reduced gas passingthrough the fluidized beds may be improved and cohesion of the ironcontaining powder may be prevented.

Also, water is supplied separately from the oxygen supply combustionsuch that the temperature of reduced gas is reduced. Hence, damage tocontents opposite the area where oxygen is supplied is prevented and thereduction ability of the reducing gas is enhanced.

With respect to the water supply nozzle of the invention, since there isused process water or steam that enables the process in the manufactureof molten iron to be easily realized, these processes may be moreefficiently performed.

Further, in the invention, in addition to performing the direct supplyof and combustion of oxygen in the fluidized beds, a separate oxygensupply apparatus is provided outside the fluidized beds such that theload with respect to oxygen supply may be lessened.

Although embodiments of the invention have been described in detailhereinabove in connection with certain exemplary embodiments, it shouldbe understood that the invention is not limited to the disclosedexemplary embodiments, but, on the contrary is intended to cover variousmodifications and/or equivalent arrangements included within the spiritand scope of the present invention, as defined in the appended claims.

1. A method for manufacturing molten iron, comprising: producing aniron-containing mixture by drying and mixing particles ofiron-containing ores and additives; passing the iron-containing mixturethrough first to third successively-connected fluidized beds in thepresence of reducing gas so that the mixture is reduced and calcined andthereby converted into a reduced material; forming a coal packed bed,which is a heat source in which the reduced material has been melted;charging the reduced material to the coal packed bed and supplyingoxygen to the coal packed bed to manufacture iron; and supplying reducedgas exhausted from the coal packed bed to the fluidized bed, whereinconverting the mixture into the reduced material comprises: (a)supplying the reducing gas to the third fluidized bed; (b) supplyingreducing gas which passed through the third fluidized bed to the secondfluidized bed; (c) supplying reducing gas which passed through thesecond fluidized bed to the first fluidized bed; (d) preheating themixture in the first fluidized bed; (e) pre-reducing the preheatedmixture in the second fluidized bed; and, (f) finally reducing thepre-reduced mixture in the third fluidized bed and converting themixture into the reduced material; wherein each fluidized bed comprisesa dispersing plate; and, wherein a stream of the reducing gas is heatedby injected oxygen gas and is partially combusted in (a) to (c), andoxygen gas is directly injected to the reducing gas that passes througha dispersing plate to be partially combusted in (d) to (f).
 2. Themethod of claim 1, wherein in converting the iron-containing mixture toa reduced material, water is supplied separately from oxygen supplycombustion process and is mixed with the oxygen.
 3. The method of claim2, wherein the water is one of process water and steam.
 4. The method ofclaim 2, wherein the water is supplied at a rate of 300˜500 Nm³/hr. 5.The method of claim 1, wherein the oxygen is supplied and combusted inthe case where an internal temperature of a fluidized-bed is 650 degreesCentigrade or higher.